Ultra high purity conditions for atomic scale processing

This application is a continuation of U.S. patent application Ser. No. 17/288,981 filed Aug. 11, 2020, which is the United States national phase of International Application No. PCT/US2020/045751 filed Aug. 11, 2020, and claims the benefit of U.S. Provisional Patent Application Nos. 62/885,446 and 63/035,014, filed Aug. 12, 2019 and Jun. 5, 2020, respectively, the disclosures of which are hereby incorporated by reference in their entireties.

The present disclosure is directed to atomic scale processing and, more particularly, to methods for reducing and/or controlling the partial pressure of background species in plasma based atomic scale processing as well as plasma based atomic scale processing under ultra-high purity (UHP) conditions.

Atomic scale processing techniques are of considerable interest for a wide range of electronic applications including logic, memory, power and optoelectronic devices. These techniques include atomic layer deposition (ALD), atomic layer etching (ALE), and area selective ALD (ASALD). Due to the surface controlled nature of atomic scale processing, maintaining a consistent, highly controlled environment is necessary for achieving consistent, reproducible process results. UHP conditions are based on reduced levels of background impurities within the process environment to reduce their role in surface reactions associated with the various atomic scale processing techniques. This includes species that contain oxygen (e.g., molecular oxygen (O) and water (HO)). UHP process conditions also provide an ideal environment for delivery and precision control of supplemental gas and/or vapor phase precursors thereby enabling enhanced atomic scale process capabilities.

ALD is a chemical vapor deposition (CVD) technique based on sequential, self-limiting surface reactions between gas/vapor phase species and active surface sites. The unique surface-controlled nature of ALD make it an ideal choice for demanding applications requiring conformal, high-quality oxide and non-oxide based materials, as well as their interfaces. For example, gate stack fabrication (i.e., high-k dielectric and metal gate) by ALD techniques for three dimensional (3D) gate-all-around field effect transistor (GAAFET) device architectures for sub-10 nm technology nodes. ALD techniques include purely thermal and plasma enhanced ALD (PEALD). A limitation associated with current PEALD reactor designs is the undesirable incorporation of oxygen during growth of non-oxide based materials, especially materials with a high affinity for oxygen, such as titanium nitride (TiN), aluminum nitride (AlN), silicon nitride (SiN), aluminum (Al), Titanium (Ti), tantalum (Ta), and the like. Due to the relatively slow deposition rates of materials grown by PEALD, non-oxide processes have long suffered from high exposures to background oxygen impurities, such as Oand/or HO, during growth yielding elevated levels of oxygen impurities in the resulting layers. UHP conditions address this longstanding issue by reducing the levels of background oxygen, as well as other impurities, to limit exposures before, during and after film growth.

In contrast to the reduction of background species, the selective addition of species (or precursors) to a UHP background can be used modify surface chemistry during ALD for enhanced process capability. These surface modifications include the removal (e.g., removal of carbon impurities) and/or incorporation (e.g., oxygen doping) of specific elements during film growth. In this case, maintaining precise control over the supplemental precursor background level is vital. For example, control of the precursor partial pressure determines the exposure and subsequent amount of material (or dopant) incorporated. Since surface chemistry drives dopant incorporation, it is necessary to maintain precise control of the precursor partial pressure to achieve the desired dopant level in the deposited film.

ALE is another atomic scale processing technique that benefits from UHP conditions. Unlike ALD techniques which are based on layer-by-layer growth, ALE techniques remove (or etch) material one layer at a time. More specifically, ALE techniques remove thin-modified surface layers with atomic scale control. At present, ALE is primarily motivated by limitations of traditional reactive ion etch (RIE) techniques for technology nodes below 10 nm. In addition to the use of ALE for defining critical device structures and patterning, a combination of ALD/PEALD and ALE techniques has been shown to effectively reduce surface roughness through growth and subsequent etch steps. For example, nucleation delay during the initial stages of growth can result in 3D island formation which leads to high surface roughness, as well as the inability to grow thin, continuous layers. Through a series of growth and etch steps, however, extremely smooth, thin, continuous layers can be achieved. Similar to ALD, the selective addition of precursors to a UHP background can also modify surface chemistry during purely thermal and plasma based ALE. These modifications include removal and/or incorporation of specific elements during surface modification and subsequent removal steps for improved etch performance.

ASALD also benefits from UHP conditions. ASALD is an ALD technique that takes advantage of differences in precursor reactivity between different starting surfaces to enable selective growth. ASALD is a bottom-up approach enabling self-alignment of features during growth thereby addressing edge placement errors associated with traditional patterning techniques. Ideally, deposition would only occur on designated growth areas, but this is frequently not the case, such that ASALD often requires a combination of ALD/PEALD and ALE process steps to ensure the desired selectivity. Therefore, the benefits of UHP conditions, including precursor delivery, are also equally applicable to ASALD.

Background impurities in atomic scale processing may originate from the following sources: system leaks, process gases, elastomer permeation, process pump back-diffusion and back-streaming, outgassing, vaporization, and/or plasma etching. A system design and related procedures must address each of these sources to obtain impurity partial pressures below 10Torr, such that UHP process conditions are achieved. For example, UHP process conditions for atomic scale processing enables background oxygen incorporation below 2 atomic % (at. %), such as below 1 at. % for non-oxide based film growth.

System leaks include atmospheric leaks, internal leaks of process gas and/or vapor across valve seats, and internal leaks due to gas/vapor trapping inside dead-space volumes and/or flow patterns that recirculate inside the reactor (generally referred to as virtual leaks). Routine leak testing of vacuum components identifies and eliminates atmospheric leaks, as well as internal leaks across valve seats. Proper design, manufacturing and assembly procedures proactively address internal leaks due to gas/vapor trapping which can be very difficult to identify.

Process gas impurities can also be a significant source of background contamination. UHP grade (99.999% purity) process gases (e.g., argon (Ar), molecular nitrogen (N), molecular hydrogen (H), etc.) can have up to parts-per-million (ppm) levels of impurities such as O, HO, carbon monoxide (CO) and carbon dioxide (CO). At typical process gas pressures ranging from 0.001 to 1 Torr, impurities at the ppm level range from 10to 10Torr partial pressure, respectively. However, improper maintenance of the source gas, delivery lines and/or components (e.g., routine gas cylinder changeover) can result in impurity concentrations exceeding the ppm level. To address the potential variability of process gas impurity levels, gas purification can be used to reduce impurities below the parts-per-billion (ppb) level thereby ensuring the requirement for UHP reactor conditions is satisfied (i.e., impurity partial pressures below 10Torr). To maintain this level of performance, however, it is important to avoid exposure of the purification media to excessive levels of contamination in the process gas which can dramatically shorten the lifetime of the purification media. For example, introduction of excessive levels of Oand/or HO from the atmosphere (or contaminated process gas from the supplier) leads to media degradation resulting in premature failure of the purifier. Therefore, periodic evaluation of the purifier is necessary to ensure performance. Baseline processes sensitive to impurity levels in the process gas are effective at determining if replacement is necessary.

A further source of background impurities in atomic scale processing is through permeation of elastomeric materials. The primary use of elastomeric materials is to create vacuum seals between system components. Elastomers contain small openings (or voids) that enable the diffusion of gases through the bulk of the elastomeric material. This diffusion of gases and/or vapors through elastomeric o-rings becomes a significant factor regarding the introduction of background impurities into the atomic scale processing environment that requires careful consideration. Elastomeric materials consist of large, interwoven molecular chains which results in a microstructure that is more susceptible to permeation compared to alternative metal seals. However, the use of metal seals, while reducing permeation, can result in an undesirable increase in vacuum system cost and complexity.

The permeation of said elastomeric materials, presented in the form of an o-ring, may be represented by the equation Q=K(A/L)ΔP with units of cm(STP)/sec (STP implies standard temperature and pressure; i.e., 0° C. (273.15 K) and 1 atm (760 Torr)), where Q is the permeation rate, K is the temperature-dependent permeation coefficient, A is the area through which gas/vapor phase species enter the elastomer, L is the thickness of the material (i.e., the permeation length), and ΔP is the difference in partial pressure across the elastomer seal for a given species. The aforementioned equation assumes steady-state diffusion and that absorbed molecules do not dissociate. In order to explicitly show temperature dependence, the steady-state permeation rate can be expressed as: Q=Ke(A/L)ΔP, where Kis a constant, E is the activation energy of diffusion, R is the gas constant, and T is the temperature (Kand E are gas and material dependent values). In general, the permeation coefficient K increases with temperature, thus increasing the permeation rate of the elastomer.

For a given elastomeric o-ring, the effective area through which gas/vapor phase species enter the elastomer may be represented by A=πDh, where D is the diameter of the o-ring and h is the compressed height. Inserting this into the aforementioned permeation rate equation yields the following approximation: Q≈K(πDh/L)ΔP, where the permeation length L is approximately the compressed width of the o-ring.

For example, let Pequal the partial pressure of water in the atmosphere at 2% atmospheric pressure (22° C., 75% relative humidity), and let Pbe the water partial pressure in an atomic scale process environment. In this case P>>Psuch that ΔP=P−P≈15 Torr. For a fluoroelastomer o-ring, such as a Viton o-ring commercially available from The Chemours Company, the temperature-dependent permeation coefficient for HO may be estimated as K≈3.7×10[(cm(STP)·gas·cm·polymer)/(cm·polymer·sec·Torr)] for the fluoroelastomer o-ring at a temperature of 150° C. A single fluoroelastomer o-ring with a diameter of D=13.6 cm (5.35 inches), d=0.50 cm (0.197 inches), h=0.40 cm (0.157 inches) and L=0.53 cm (0.209 inches), the permeation rate Qwould equal 1.8×10cm(STP)/sec (or 2.1×10Torr·Liters/sec). For an effective pumping speed Sof 21 Liters/sec, the background water partial pressure Pis ˜10Torr (P=Q/S), or ˜1 Langmuir exposure every second. In order to achieve UHP conditions, background impurities due to elastomeric permeation must be reduced below 10Torr partial pressure.

Another source of background impurities and contamination is process pump back-diffusion and back-streaming of atmosphere, and other impurities condensed and/or deposited inside the pump. Oil-sealed mechanical pumps include pump oil, as well as pump oil vapors as potential sources of impurities. Pump oils generally contain hydrocarbon species and, in the case of perfluoropolyether type oils, contain carbon, fluorine, and oxygen. Although dry mechanical pumps may be implemented to eliminate pump oil concerns, said pumps still generate back-diffusion/streaming of impurities condensed and/or deposited on internal pump surfaces.

Additional sources of background impurities are outgassing and vaporization. Outgassing/vaporization can also be considered as another type of virtual leak. Outgassing includes desorption of species absorbed on internal surfaces from one to several layers thick which can be thermally activated, or stimulated by alternative energy sources, such as plasma exposure. Outgassing further refers to diffusion and subsequent desorption of absorbed elements or compounds within reactor walls and internal fixtures. Vaporization includes the transition of a liquid or solid phase substance to the vapor phase. For liquids and solids, vaporization may also be referred to as evaporation and sublimation, respectively. In general, outgassing and vaporization rates increase with an increase in temperature.

During atomic scale processing, liquid and/or solid phase precursors (or reactants) are routinely vaporized and transported via delivery source to a reaction space containing a substrate. A vapor delivery arrangement generally includes a precursor ampoule, valving, and a line to the reactor including stainless-steel tubing and various metal seal connections. Moreover, a vapor delivery arrangement also includes means of providing continuous, viscous-laminar inactive gas flow through the vapor delivery channel. For example, a mass flow controller (MFC) may be used to control the continuous flow of inactive Ar or Nprocess gas through the valving and the line to the reactor. Continuous, viscous-laminar inactive gas flow serves as a carrier gas during precursor delivery/dose steps, and as a purge gas during subsequent purge steps. This inactive gas flow also creates a diffusion barrier to prevent unwanted back-diffusion of downstream impurities into the vapor delivery channel. In addition to continuous, viscous-laminar flow of inactive carrier/purge gas, heating of delivery source components is essential to prevent long residence times due to precursor adsorption, as well as condensation (vapor-to-liquid transition) or deposition (vapor-to-solid transition) within the delivery channel. In many cases, effective vapor delivery also requires heating of the liquid/solid phase precursor itself to increase its vapor pressure. During precursor dose and purge steps, the temperature must be sufficiently high and uniform to minimize the residence time within the delivery channel. If purging is not complete between precursor dose steps, outgassing/vaporization of material within the delivery channel results in an unwanted source of background impurities where related issues include parasitic chemical vapor deposition effects, particulates, clogging of delivery components and process cross contamination. Process cross contamination results in unwanted impurities in films grown by ALD/PEALD techniques. Careful heating of the delivery components helps to avoid these common issues.

A further source of background impurities is plasma etching. Plasma source design and its construction are important considerations in plasma based atomic scale processing. Common plasma configurations include direct and remote capacitively coupled plasma (CCP), and remote inductively coupled plasma (ICP) designs. Inductive, radio frequency (RF) sources operating at 13.56 megahertz (MHz) are routinely used to generate plasma in atomic scale processing. Remote ICP sources provide good plasma uniformity and a modular design for ease of service. Further, remote ICP sources have an external located electrode to eliminate the potential for etching of the metallic surface. However, chemical and/or physical (or sputter) etching of the dielectric surfaces used for signal transmission can be a source of background impurities. Fused silica is a common dielectric material for RF signal transmission; however, the use of fused silica may result in etching of the dielectric surface which is a source of oxygen and silicon background impurities.

In general, background impurity levels may be substantially reduced by lowering the base pressure of the vacuum apparatus (or reactor) used for growth and/or etch by atomic scale processing techniques. More specifically, the reactor base pressure may be lowered by increasing the pumping speed of the pump used for achieving process vacuum according the relationship P=Q/Swhere P is the reactor pressure (Torr), Q is the throughput (Torr·Liters/sec) and Sis the effective pumping speed (Liters/sec). The base pressure corresponds to the vacuum level in the reactor without any process gas actively flowing. In this case, the pressure P is the sum of all background component partial pressures, which is proportional to the associated throughput Q. The proportionality constant is (1/S) such that increasing the effective pumping speed lowers the base pressure in the reactor. Mechanical pumps enable a minimum base pressure of approximately 10to 10Torr. To achieve a base pressure below 10Torr, turbomolecular pumps are commonly utilized. If sufficient gas flow and reactor pressure are not maintained during processing, however, unwanted precursor exposure and subsequent film deposition on critical/sensitive surface inside the reactor may occur. Unwanted deposition occurs as a result of an insufficient diffusion barrier to protect critical/sensitive surfaces during precursor dose and purge steps. For example, deposition of a thin, highly conductive TiNlayer on dielectric surfaces used for RF signal transmission during PEALD results in signal attenuation followed by loss of plasma.

Diffusion barrier performance is highly dependent on geometry, pressure and gas flow rate. To create an effective diffusion barrier, gas flow must be viscous and laminar. A general requirement for viscous flow is that characteristic reactor dimensions (e.g., cylindrical tube diameter) should exceed ˜100× the mean free path λ of the background process gas. For Ar process gas at 1 Torr pressure (gas temperature=150° C.) the mean free path is ˜0.003 inches (0.08 mm). In this case, characteristic dimensions of the reactor should be >0.3 inches (0.8 cm) to ensure viscous flow conditions. If the pressure is reduced to 0.1 Torr, then critical reactor dimensions should exceed 3 inches (8 cm). For cylindrical, or tubular, reactor geometries at 0.1 Torr pressure, the diameter should exceed 3 inches to ensure the flow is viscous. Typical reactors for atomic scale processing, therefore, require process pressures exceeding a few hundred mTorr to ensure viscous flow conditions through the reactor, as well as associated ports/features (e.g., ports/features for substrate transfer, in-situ ellipsometry and inductive plasma). For process pressures above approximately 100 mTorr (0.1 Torr), turbomolecular pumping speeds dramatically decrease to levels at or below typical mechanical pumps with pumping speeds ranging from approximately 5 to 50 Liters/sec. In addition to gas flow that is viscous, the flow rate must be high enough to prevent back-diffusion of unwanted species within the channel. At pressures required for viscous flow (e.g., above 0.2-0.3 Torr), as well as gas flow rates necessary to create an effective diffusion barrier, mechanical pumps have the advantage of maintaining their pumping speed with minimal variation. Finally, viscous flow is laminar (vs. turbulent) when the Reynold's number is below 1100 (i.e., R<1100). Based on typical atomic scale process conditions (i.e., temperatures, gas flow rates, pressures), R<<1100 for cylindrical geometries thereby satisfying the condition for viscous-laminar flow.

Therefore, a method for reducing and/or controlling the partial pressure of background species in atomic scale processing, including the reduction of background species caused by any of the aforementioned sources of background impurities, is desirable. Additionally, an atomic scale processing apparatus that includes components for reducing and/or controlling the partial pressure of background species during processing is also desirable.

In view of the foregoing, there is a current need in the art for a method to reduce and/or control the partial pressure of background species during atomic scale processing. In further view of the foregoing, there is a current need in the art for an atomic scale processing apparatus with reduced background species (or impurities), as well as the ability to selectively add species (or precursors) to modify surface chemistry thereby enhancing atomic scale process capabilities.

In one non-limiting example of the present disclosure, an apparatus for atomic scale processing includes: a reactor having inner and outer surfaces; where at least a portion of the inner surfaces define an internal volume of the reactor; a fixture assembly positioned within the internal volume of the reactor having a surface configured to hold a substrate within the internal volume of the reactor; and an inductively coupled plasma source; where the inductively coupled plasma source and the reactor are connected at a first connection point; where the first connection point comprises a first elastomeric seal and a second elastomeric seal spaced apart from the first elastomeric seal to define a first volume therebetween; and where the first volume is a vacuum, or the first volume is actively purged and/or backfilled with a process gas.

The apparatus may further include a process gas source; where the process gas source and the inductively coupled plasma source are connected at a second connection point; where the second connection point comprises a third elastomeric seal and a fourth elastomeric seal spaced apart from the third elastomeric seal to define a second volume therebetween; and where the second volume is a vacuum, or the second volume is actively purged and/or backfilled with a process gas. A continuous, inactive gas flow may be maintained from the process gas source to the ICP source and the reactor. The inductively coupled plasma source may include a cooling arrangement; where the cooling arrangement provides active cooling at the first and second connection points. The cooling arrangement may include one or more heat sinks. The cooling arrangement may include one or more water-cooled base plates. The cooling arrangement may include one or more water-cooled mounting flanges. The cooling arrangement may include a cooling fan. The cooling arrangement may include one or more water-cooled enclosure panels. The apparatus may be configured such that all remaining connection points spatially located between the first connection point and the fixture assembly include metallic and/or elastomeric seals; where each elastomeric seal connection point includes at least two elastomeric seals spaced apart to define a volume therebetween; and where the volume is a vacuum, or the volume is actively purged and/or backfilled with a process gas. The apparatus may include an exhaust port from the reactor to a pump isolation valve and a foreline from the pump isolation valve to a pump; where a continuous gas flow is maintained in the exhaust port and the foreline when the pump is on, the pump isolation valve is open, and the reactor is in communication with the pump. The apparatus may include a downstream port attached to the foreline; where the downstream port is configured to provide continuous gas flow to the foreline when the pump is on, the pump isolation valve is closed, and the reactor is not in communication with the pump. The downstream port may be further configured to provide gas flow that rapidly brings the foreline to atmospheric pressure when the pump isolation valve is closed and the pump is turned off. The inductively coupled plasma source may include a dielectric tube, and where the dielectric tube comprises fused silica, ceramic alumina, sapphire, or a combination thereof. The apparatus may further include at least one precursor vapor delivery arrangement in communication with the reactor. A continuous, inactive gas flow may be maintained from the at least one precursor vapor delivery arrangement to the reactor. At least one of the at least one precursor vapor delivery arrangements may include a cladding around at least a portion of the precursor vapor delivery arrangement. The cladding may be aluminum cladding, or some other suitable thermal mass with sufficient thermal conductivity. At least one of the at least one precursor vapor delivery arrangements may include at least one heater jacket, or some other suitable means of supplying thermal energy, around at least a portion of the precursor vapor delivery arrangement. At least one of the at least one precursor vapor delivery arrangements may include at least one independently controlled heat zone. The reactor may include a cladding around at least a portion of the reactor. The cladding may be aluminum cladding, or some other suitable thermal mass with sufficient thermal conductivity. The reactor may include at least one heater jacket, or some other suitable means of supplying thermal energy, around at least a portion of the reactor. The reactor may include at least one independently controlled heat zone. The apparatus may further include at least one gas purification arrangement between the reactor and at least one source of process gas. The apparatus may further include a mechanical pump with a nominal pumping speed of approximately 5 to 50 Liters/sec. A base pressure of the reactor may be between approximately 10and 10Torr. A partial pressure of each background impurity within the internal volume of the reactor may be below approximately 10Torr to reduce said background impurities role in surface reactions before, during, and after atomic scale processing. The apparatus may further include at least one precursor gas or vapor delivery arrangement for supplying a precursor gas or vapor to the internal volume of the reactor, and controlling the background partial pressure of said precursor gas and vapor, including: a compressed gas cylinder or an ampoule; a reservoir and pressure gauge in communication with the compressed gas cylinder or the ampoule and the reactor; where a regulator, a first orifice, and a first valve are provided between the compressed gas cylinder or the ampoule and the reservoir and pressure gauge; system control software in communication with the pressure gauge and the first valve; where the system control software receives feedback from the pressure gauge and cycles the first valve based on said feedback to control flow from the compressed gas cylinder or the ampoule into the reservoir; where a second orifice and a second valve are provided between the reservoir, pressure gauge and the reactor to control the flow of the precursor gas or vapor from the reservoir to the reactor. The apparatus may further include at least one precursor gas or vapor delivery arrangement for supplying a precursor gas or vapor to the internal volume of the reactor, and controlling the background partial pressure of said precursor gas or vapor, including: a compressed gas cylinder or an ampoule in communication with the reactor; where a regulator, an orifice, and a valve are provided between the compressed gas cylinder or the ampoule and the reactor to control the flow of precursor gas or vapor from the compressed gas cylinder or the ampoule to the reactor. The apparatus may further include at least one precursor vapor delivery arrangement for supplying a precursor vapor to the internal volume of the reactor, and controlling the background partial pressure of said precursor vapor, including: an ampoule in communication with the reactor; where an orifice and a valve are provided between the ampoule and the reactor to control the flow of precursor vapor from the ampoule to the reactor.

In another non-limiting example of the present disclosure, a method of reducing background impurities during atomic scale processing includes: providing a reactor having inner and outer surfaces, where at least a portion of the inner surfaces define an internal volume of the reactor; providing a fixture assembly positioned within the internal volume of the reactor having a surface configured to hold a substrate within the internal volume of the reactor; providing a first elastomeric seal and a second elastomeric seal at a first connection point between an inductively coupled plasma source and the reactor; establishing a first volume defined between the first elastomeric seal and second elastomeric seal; and applying a vacuum to the first volume, or actively purging and/or backfilling the first volume with a process gas, to lower an atmospheric partial pressure within the first volume.

The method may further include providing a third elastomeric seal and a fourth elastomeric seal at a second connection point between the inductively coupled plasma source and a process gas source; establishing a second volume defined between the third elastomeric seal and the fourth elastomeric seal; and applying a vacuum to the second volume, or actively purging and/or backfilling the second volume with a process gas, to lower an atmospheric partial pressure within the second volume. The method may further include maintaining a continuous, inactive gas flow from the process gas source to the ICP source and the reactor. The method may further include providing a cooling arrangement in the inductively coupled plasma source which provides active cooling to prevent thermal damage to the elastomeric seals at the first and second connection points. The cooling arrangement may include one or more heat sinks. The cooling arrangement may include one or more water-cooled base plates. The cooling arrangement may include one or more water-cooled mounting flanges. The cooling arrangement may include a cooling fan. The cooling arrangement may include one or more water-cooled enclosure panels. The method may further include providing metallic and/or elastomeric seals at all remaining connection points spatially located between the first connection point and the fixture assembly; where each elastomeric seal connection point includes at least two elastomeric seals spaced apart to define a volume therebetween; and where the volume is a vacuum, or the volume is actively purged and/or backfilled with a process gas, to lower an atmospheric partial pressure within the volume. The method may further include providing an exhaust port in communication with the reactor and a pump isolation valve; providing a foreline in communication with the pump isolation valve and a pump; and maintaining a continuous gas flow in the exhaust port and the foreline when the pump is on, the pump isolation valve is open, and the reactor is in communication with the pump to prevent back-diffusion of impurities from the foreline and/or pump into the internal volume of the reactor. The method may further include establishing a downstream port in communication with the foreline; and maintaining continuous gas flow to the foreline when the pump is on, the pump isolation valve is closed, and the reactor is not in communication with the pump to prevent back-diffusion of impurities from the pump into the foreline. The method may further include providing gas flow which rapidly brings the foreline to atmospheric pressure when the pump isolation valve is closed and the pump is turned off to prevent back-streaming of impurities from the pump into the foreline. The inductively coupled plasma source may include a dielectric tube, where the dielectric tube may include fused silica, ceramic alumina, sapphire, or a combination thereof to substantially eliminate etching of the dielectric tube surface. The method may further include establishing communication between at least one precursor vapor delivery arrangement and the reactor. The method may further include maintaining a continuous, inactive gas flow from the at least one precursor vapor delivery arrangement to the reactor. At least one of the at least one precursor vapor delivery arrangements may include cladding around at least a portion of the precursor vapor delivery arrangement. The cladding may be aluminum cladding, or some other suitable thermal mass with sufficient thermal conductivity. At least one of the at least one precursor vapor delivery arrangements may include at least one heater jacket, or some other suitable means of supplying thermal energy, around at least a portion of the precursor vapor delivery arrangement. The method may further include establishing at least one independently controlled heat zone on at least one of the at least one precursor vapor delivery arrangements to substantially reduce the residence time of precursor vapors on surfaces within the precursor vapor delivery arrangement. The reactor may include a cladding around a least a portion of the reactor. The cladding may be aluminum cladding, or some other suitable thermal mass with sufficient thermal conductivity. The reactor may include at least one heater jacket, or some other suitable means of supplying thermal energy, around at least a portion of the reactor. The method may further include establishing at least one independently controlled heat zone to substantially reduce the residence time of precursor gases, vapors and/or reaction byproducts on surfaces within the internal volume of the reactor. The method may further include providing at least one gas purification arrangement between the reactor and at least one source of process gas to substantially reduce said process gas impurity levels. The method may further include providing a mechanical pump with a nominal pumping speed of approximately 5 to 50 Liters/sec. A base pressure of the reactor may be between approximately 10and 10Torr. A partial pressure of each background impurity within the internal volume of the reactor may be below approximately 10Torr.

In another non-limiting example of the present disclosure, a method of selectively adding precursor gas or vapor to an ultra-high purity background and controlling the partial pressure of said precursor gas or vapor includes: providing a reactor for atomic layer processing; providing at least one supplemental precursor gas or vapor delivery arrangement in communication with the reactor; establishing an ultra-high purity level within an internal volume of the reactor; selectively adding precursor gas or vapor into the internal volume of the reactor once the ultra-high purity level has been achieved; and controlling a background partial pressure of said precursor gas or vapor within the internal volume of the reactor.

In another non-limiting example of the present disclosure, an apparatus for supplying precursor gas or vapor to an ultra-high purity background and controlling the partial pressure of said precursor gas or vapor includes: a reactor having inner and outer surfaces; where at least a portion of the inner surfaces define an internal volume of the reactor, and where an ultra-high purity level is established within the internal volume of the reactor; a fixture assembly positioned within the internal volume of the reactor having a surface configured to hold a substrate within the internal volume of the reactor; at least one primary precursor gas or vapor delivery arrangement; and at least one supplemental precursor gas or vapor delivery arrangement.

The at least one primary precursor gas or vapor delivery arrangement may be configured to sequentially supply the reactor with a precursor gas or vapor, and the supplemental precursor gas or vapor delivery arrangement may be configured to continuously supply the reactor with a precursor gas or vapor. The at least one supplemental precursor gas or vapor delivery arrangement may include: a compressed gas cylinder or an ampoule in communication the reactor; and a reservoir and pressure gauge between the compressed gas cylinder or the ampoule and the reactor. The at least one supplemental precursor gas or vapor delivery arrangement may further include: a regulator between the compressed gas cylinder or the ampoule and the reservoir and pressure gauge; a first orifice between the regulator and the reservoir and pressure gauge; and a first valve between the first orifice and the reservoir and pressure gauge. The at least one supplemental precursor gas or vapor delivery arrangement may further include: a second orifice between the reservoir and pressure gauge and the reactor; and a second valve between the second orifice and the reactor; where the second orifice and the second valve control the flow of precursor gas or vapor from the reservoir to the reactor. The apparatus may further include system control software in communication with the pressure gauge and the first valve; where the system control software receives feedback from the pressure gauge and cycles the first valve based on the feedback to control flow into the reservoir. The at least one supplemental precursor gas or vapor delivery arrangement may include: a compressed gas cylinder or an ampoule in communication the reactor; where a regulator, an orifice, and a valve are provided between the compressed gas cylinder or ampoule and the reactor to control the flow of a precursor gas or vapor from the compressed gas cylinder or the ampoule to the reactor. The at least one supplemental precursor vapor delivery arrangement may further include: an ampoule in communication with the reactor; where an orifice and a valve are provided between the ampoule and the reactor to control the flow of precursor vapor from the ampoule to the reactor.

Various preferred and non-limiting examples or aspects of the present invention will now be described and set forth in the following numbered clauses:

Clause 1: an apparatus for atomic scale processing comprises: a reactor having inner and outer surfaces; wherein at least a portion of the inner surfaces define an internal volume of the reactor; a fixture assembly positioned within the internal volume of the reactor having a surface configured to hold a substrate within the internal volume of the reactor; and an inductively coupled plasma source; wherein the inductively coupled plasma source and the reactor are connected at a first connection point; wherein the first connection point comprises a first elastomeric seal and a second elastomeric seal spaced apart from the first elastomeric seal to define a first volume therebetween; and wherein the first volume is a vacuum, or the first volume is actively purged and/or backfilled with a process gas.

Clause 2: the apparatus of clause 1, further comprising: a process gas source; wherein the process gas source and the inductively coupled plasma source are connected at a second connection point; wherein the second connection point comprises a third elastomeric seal and a fourth elastomeric seal spaced apart from the third elastomeric seal to define a second volume therebetween; and wherein the second volume is a vacuum, or the second volume is actively purged and/or backfilled with a process gas.

Clause 3: the apparatus of clause 2, wherein the inductively coupled plasma source comprises a cooling arrangement; wherein the cooling arrangement provides active cooling at the first and second connection points.

Clause 4: the apparatus of clause 3, wherein the cooling arrangement comprises one or more heat sinks.

Clause 5: the apparatus of any of clauses 3-4, wherein the cooling arrangement comprises one or more water-cooled base plates.

Clause 6: the apparatus of any of clauses 3-5, wherein the cooling arrangement comprises one or more water-cooled mounting flanges.

Clause 7: the apparatus of any of clauses 3-6, wherein the cooling arrangement comprises a cooling fan.

Clause 8: the apparatus of any of clauses 3-7, wherein the cooling arrangement comprises one or more water-cooled enclosure panels.

Clause 9: the apparatus of any of clauses 1-8, wherein all remaining connection points spatially located between the first connection point and the fixture assembly comprise metallic and/or elastomeric seals; wherein each elastomeric seal connection point comprises at least two elastomeric seals spaced apart to define a volume therebetween; and wherein the volume is a vacuum, or the volume is actively purged and/or backfilled with a process gas.

Clause 10: the apparatus of any of clauses 1-9, further comprising an exhaust port from the reactor to a pump isolation valve and a foreline from the pump isolation valve to a pump; wherein a continuous gas flow is maintained in the exhaust port and the foreline when the pump is on, the pump isolation valve is open, and the reactor is in communication with the pump.

Clause 11: the apparatus of clause 10, further comprising a downstream port attached to the foreline; wherein the downstream port is configured to provide continuous gas flow to the foreline when the pump is on, the pump isolation valve is closed, and the reactor is not in communication with the pump.

Clause 12: the apparatus of clause 11, wherein the downstream port is further configured to provide gas flow that rapidly brings the foreline to atmospheric pressure when the pump isolation valve is closed and the pump is turned off.

Clause 13: the apparatus of any of clauses 1-12, wherein the inductively coupled plasma source comprises a dielectric tube, and wherein the dielectric tube comprises fused silica, ceramic alumina, sapphire, or a combination thereof.

Clause 14: the apparatus of any of clauses 1-13, further comprising at least one precursor vapor delivery arrangement in communication with the reactor.

Clause 15: the apparatus of clause 14, wherein at least one of the at least one precursor vapor delivery arrangements comprises a cladding around at least a portion of the precursor vapor delivery arrangement.

Clause 16: the apparatus of clause 15, wherein the cladding is aluminum cladding, or some other suitable thermal mass with sufficient thermal conductivity.

Clause 17: the apparatus of any of clauses 14-16, wherein at least one of the at least one precursor vapor delivery arrangements comprises at least one heater jacket, or some other suitable means of supplying thermal energy, around at least a portion of the precursor vapor delivery arrangement.

Clause 18: the apparatus of any of clauses 14-17, wherein at least one of the at least one precursor vapor delivery arrangements comprise at least one independently controlled heat zone.

Clause 19: the apparatus of any of clauses 1-18, wherein the reactor comprises a cladding around at least a portion of the reactor.

Clause 20: the apparatus of clause 19, wherein the cladding is aluminum cladding, or some other suitable thermal mass with sufficient thermal conductivity.